1. Field of the Invention
This invention generally relates to a magnetic head for use in a magnetic recording and reproducing apparatus, and more particularly to a thin film magnetic head for use in an analog magnetic recording and reproducing apparatus and a digital magnetic recording and reproducing apparatus.
2. Description of the Related Art
In recent years, a demand for larger memory capacity has sprung up. This demand has been met by increasing the track recording density of data recorded by a magnetic head. A thin film magnetic head has been devised and adapted for use as a magnetic head which satisfies theses high density requirements. A conventional thin film magnetic head, however, suffers from the fact that it must go through many processes, such as a a thin film production process, a photolithographic process and an etching process. Furthermore, an annealing process is necessary for stabilizing the crystal structure of the thin film. The special advantage associated with using the thin film technique cannot be fully utilized because a great number of thin film magnetic heads cannot be produced in large quantities.
Further, in recent years, there has been devised a thin film magnetic head having a multi-track structure for use in a magnetic recording and reproducing apparatus using a magnetic tape which is produced by first forming a coil layer on a magnetic substrate by use of the thin film technique, and then covering this coil layer with another ferrite substrate. In the case of the thin film magnetic head of this type, the coil layer is formed by a thin film. Thus, the width of a track can be substantially reduced. Further, because the thin film magnetic head has a simple structure, production thereof can be increased.
Hereinafter, this conventional thin film magnetic head will be explained by referring to FIGS. 6 and 7.
FIG. 6 is a sectional side view of the conventional thin film magnetic head. Further, FIG. 7 is a top view of the conventional thin film magnetic head of FIG. 6. In these figures, reference numeral 1 indicates a lower magnetic block made of nonconductive magnetic material. In the conventional thin film magnetic head, Ni-Zn ferrite is mainly employed as the nonconductive magnetic material. Further, reference numeral 2 indicates the coil layer formed on the lower magnetic block 1 in the following manner. First, a conductive film made of materials such as Cu and Au is formed on the lower magnetic block 1 by using a vapor deposition method or a sputtering method. Thereafter, the coil layer 2 is formed by forming the conductive film into a predetermined shape thereof by performing a method such as photolithography. At that time, there is provided a gap 6, of which the width is sufficient to contain a film made of gap filler therein, between an upper magnetic block 5 (to be described later) and the combination of the coil layer 2 and an insulating layer 3 (also to be described later). Furthermore, reference numeral 3 indicates an insulating layer formed on a part of the surface of the lower magnetic block 1 other than the part on which the coil layer 2 is formed. Further, the thickness of the insulating layer is arranged to be almost equal to that of the coil layer 2. This insulating layer 3 is made of an oxide such as SiO.sub.2 or Al.sub.2 O.sub.3 by using the sputtering method. Moreover, reference numeral 4 indicates a lead mounted don the insulating layer 3 in such a manner that it strides over the coil layer 2. Furthermore, another insulating layer 4a is provided between the lead 4 and the coil layer 2. Reference numeral 5 indicates an upper magnetic block connected to the coil layer 2 and the insulating layer 3 by an epoxy resin adhesive agent. In this upper magnetic block 5, a track limiting groove 5a for limiting the width of a track is formed as shown in FIG. 8 and this groove is filled with glass. Further, another groove 5b is bored in such a manner to extend in the direction perpendicular to the track limiting groove 5a and is also filled with glass. Also shown in FIG. 6 is storage medium 14. In the thus constructed thin film magnetic head, magnetic induction, which is represented by using magnetic lines of flux indicated by arrows shown in FIG. 6, is induced. Moreover, in the thus constructed thin film magnetic head, a magnetic layer is formed by the magnetic blocks in place of a thin film. Therefore this thin film magnetic head excels in productivity.
However, in the above described conventional thin film magnetic head, an end of the upper magnetic block 5 is placed as close as possible to the lead 4 and the upper magnetic block 5 is connected to the top surface of the coil layer 2 by the epoxy resin adhesive agent such that the upper magnetic block 5 does not overlap with the lead 4 and the magnetic flux generated in the coil layer 2 efficiently flows through the upper magnetic block 5 and the lower magnetic block 1. It is, however, difficult to conduct such an operation and thus this has caused difficulty in further increasing the productivity of the thin film magnetic head.
Further, in the insulating layer 4a provided on the coil layer 2 to insulate the lead 4 from the coil layer 2, a part of the insulating layer 4a corresponding to an edge portion of the coil layer 2 is extremely thin. Thus, the conventional thin film magnetic head has another drawback in that an insulation failure is apt to occur at that part thereof.
The present invention is accomplished to eliminate the above described defects of the conventional thin film magnetic head.